Parathyroid disease is conventionally divided into states where the parathyroid is overactive (
hyperparathyroidism), and states where the parathyroid is under- or hypoactive (
hypoparathyroidism). Both states are characterised by their symptoms, which relate to the excess or deficiency of
parathyroid hormone in the blood.
Hyperparathyroidism Primary Hyperparathyroidism is the state in which there is excess parathyroid hormone circulating in the blood. This may cause bone pain and tenderness, due to increased
bone resorption. With increased circulating calcium, there may be other symptoms associated with
hypercalcemia, most commonly dehydration. Hyperparathyroidism is most commonly caused by a benign proliferation of chief cells in one parathyroid gland, and rarely in
MEN syndrome. This is known as
primary hyperparathyroidism,
Secondary Renal disease may lead to hyperparathyroidism. When too much calcium is lost from the blood via urination, there is a compensation by the parathyroid, and parathyroid hormone is released. The glands enlarge (hypertrophy) to synthesize more parathyroid hormone. This is known as
secondary hyperparathyroidism.
Tertiary If secondary hyperparathyroidism persists over months, the parathyroid tissue may become unresponsive to the blood calcium levels, and begin to autonomously release parathyroid hormone. This is known as
tertiary hyperparathyroidism.
Hypoparathyroidism The state of decreased parathyroid activity is known as hypoparathyroidism. This is most commonly associated with damage to the glands or their blood supply during
thyroid surgeryit may be associated with rarer genetic syndromes such as
DiGeorge syndrome, which is inherited as an
autosomal dominant syndrome. Hypoparathyroidism will occur after surgical removal of the parathyroid glands. Occasionally, an individual's tissues are resistant to the effects of parathyroid hormone. This is known as
pseudohypoparathyroidism. In this case, the parathyroid glands are fully functional. However, the hormone itself is not able to function, resulting in a decrease in blood calcium levels. Pseudohypoparathyroidism is often associated with the genetic condition
Albright's hereditary osteodystrophy. Pseudo-pseudohypoparathyroidism, one of the
longest words in the English language, is used to describe an individual with Albright's hereditary osteodystrophy with normal parathyroid hormone and serum calcium levels. Hypoparathyroidism may present with symptoms associated with
decreased calcium, and is generally treated with
Vitamin D analogues. ==History==